This invention relates to containers, tanks, or ships, for the storage or transportation of cryogenic liquids such as liquid natural gas (LNG), and is particularly concerned with containers, tanks or ships of the above type containing non-metallic, e.g. plastic, foam insulation and one or more liners, and preferably a low temperature resisting, e.g. low thermal expansion, liner such as high nickel steel, and a simple yet strong support structure for the liner or membrane at the corners, such corner structure being readily fitted into the foam insulation at the corner and permitting transmission of loads at various angles from the liner to the tank wall or ship hull, with minimum heat transmission to the cold contents.
A container or tanker for the storage and/or transportation of a cryogenic liquid must be designed to withstand extremely cold temperatures. Generally vessels of this type are composed of an outer wall of a rigid structure, a heat insulating layer provided at the inside surface of such wall and an inner membrane on the inside surface of such heat insulating layer. Often several heat insulating layers of non-metallic, e.g. plastic, foam insulation, are employed and one or more membranes, particularly an inner liner or membrane such as a nickel steel liner in contact with the cryogenic liquid and one or more additional secondary liners positioned between foam insulating layers. The primary liner, generally made of a thin low temperature resistant (low thermal expansion) material such as nickel steel, is maintained in close contact with the surface of the adjacent heat insulating layer and transmits the internal pressure applied by the low temperature liquefied gases through the heat insulating layers to the outer container or the hull of a tanker. Illustrative of such a system is U.S. Pat. No. 3,814,275, to Lemons.
Of particular importance, the container or its insulation system must be capable of withstanding the thermal strains induced by the cold liquid and the transients during the cooling and warming cycles caused by the loading and unloading of the liquid, and the mechanically induced strains from the ship hull or container displacement during operation.
Critical portions of such cryogenic insulation systems for supporting the primary liner are at the corners where loads to which the liner is subjected, are transmitted to the container wall or ship hull. In membrane systems of the above type, designed to contain cryogenic liquids, the corners must be secured against movement caused by membrane contraction and deflection of the supporting structure. Such corner structures must resist loads at various angles and in a number of different directions with minimum heat transmission to the cold cargo.
Various corner designs for insulated cryogenic containers or ships have been developed in the prior art. Exemplary of such structures are those disclosed in Gilles, U.S. Pat. No. 3,399,800; Helf et al., No. 3,931,424; and Clarke et al. No. 3,337,079.
Also, in applications Ser. Nos. 665,285, filed Mar. 9, 1976 of McCown, now U.S. Pat. No. 4,116,150 and 759,910, filed Jan. 17, 1977 of McCown, now U.S. Pat. No. 4,170,952 and assigned to the same assignee as the present application, there are disclosed cryogenic insulation systems containing corner structures including tubular couplers and associated structure for connecting the liner to the container wall or ship hull at the corners.
However, one of the main difficulties of the relatively complex corner structures of the prior art is the difficulty involved in fitting the cryogenic insulation around the various components forming these corner structures, involving the use of intricate specially cut pieces of foam for this purpose, which substantially increases the cost of such cryogenic insulation systems.